Subsea systems, such as those used in exploration and production of oil and gas, continue to increase in complexity. A subsea well can include sensors and actuators located at or below the sea floor. The sensors can be, for example, pressure sensors, temperature sensors, and erosion detectors. The actuators can be, for example, valves, pumps, and other flow control devices. Information from the sensors is commonly communicated with other subsea facilities and then communicated with or processed by equipment at a surface facility. Similarly, controls for the actuators commonly originate at a surface facility. Accordingly, communication is needed between the subsea devices and equipment at the surface.
In offshore drilling and production operations, equipment are often subjected to harsh conditions thousands of feet under the sea surface with working temperatures of −50° F. to 350° F. with pressures of up to 15,000 psi. Subsea control and monitoring equipment commonly are used in connection with operations concerning the flow of fluid, typically oil or gas, out of a well. Flow lines are connected between subsea wells and production facilities, such as a floating platform or a storage ship or barge. Subsea equipment include sensors and monitoring devices (such as pressure, temperature, corrosion, erosion, sand detection, flow rate, flow composition, valve and choke position feedback), and additional connection points for devices such as down hole pressure and temperature transducers. A typical control system monitors, measures, and responds based on sensor inputs and outputs control signals to control subsea devices. For example, a control system attached to a subsea tree controls down-hole safety valves. Functional and operational requirements of subsea equipment have become increasingly complex along with the sensing and monitoring equipment and control systems used to insure proper operation.
To connect the numerous and various sensing, monitoring and control equipment necessary to operate subsea equipment, harsh-environment connectors are used with electrical cables, optical fiber cables, or hybrid electro-optical cables. There exists a variety of wet-mate and dry-mate electrical and optical connectors that may be employed in subsea communication systems. In some known underwater electrical connectors, such as that described in U.S. Pat. Nos. 4,616,900; 4,682,848; 4,795,359; 5,194,012; 5,838,857; 6,315,461; 6,736,545; and 7,695,301, by Cairns, each of which is incorporated by reference herein in their entirety. Other known seal mechanisms involve some type of rotating seal element along with an actuator for rotating the seal element between a closed, sealed position when the units are unmated, and an open position when the units are mated, allowing the contact probes to pass through the seal elements into the contact chambers. Such connectors are described, for example, in U.S. Pat. Nos. 5,685,727 and 5,738,535 of Cairns, which are incorporated by reference herein in their entirety. The contacts on one side of a subsea or wet mateable electrical connector are typically in the form of pins or probes, while the contacts or junctions on the other side are in the form of sockets for receiving the probes. Typically, the socket contacts are contained in a sealed chamber containing a dielectric fluid or other mobile substance, and the probes enter the chamber via one or more sealed openings which include seals which exclude seawater and/or contaminants from the contact chamber in the mated and unmated conditions. Such electrical connectors are generally known as pin-and-socket type connectors. One example of an electrical underwater pin and socket connector is described in SEALED, FLUID-FILLED ELECTRICAL CONNECTOR, Cairns, U.S. Pat. No. 5,645,442, issued Jul. 8, 1997, and is sold by Teledyne ODI, Inc. of Daytona Beach, Fla. under the name Nautilus® and is incorporated by reference herein in its entirety.
To facilitate communication between these underwater devices, and between different communication mediums and network types, systems and control device are employed to manage the subsea equipment. Subsea communication may be implemented by fiber optic, electrical, or hybrid optical-electric communication systems. Fiber optic communication systems typically employ one or more optical fibers, while electrical communication systems employ copper wire which may be implemented as a twisted pair. Communication between devices and pieces of equipment may be on a TCP/IP network and may be handled by one or more modems, switches, routers, and control apparatuses.
Controller area network (“CAN”) buses are used to interconnect sensors, actuators, controllers, and other devices in applications such as automobiles, industrial automation, and medical equipment. Many circuits and devices have been developed for CAN BUS communications. However, current CAN BUS based subsea systems face several limitations. Network size is restricted due to the impedance drop that results from connecting multiple electrical devices in parallel. Additionally, conventional driver components may not be suitable for long transmission lines. One system and method for controlling optical CAN BUS systems is described in SYSTEMS AND METHODS FOR SUBSEA OPTICAL CAN BUSES, Xi, U.S. Pat. No. 9,057,846, issued Jun. 16, 2015, and one cable that may be used in such a system is described in SUBSEA ELECTRO-OPTICAL CONNECTOR UNIT FOR ELECTRO-OPTICAL ETHERENET TRANSMISSION SYSTEM, Nagengast et al., U.S. Pat. No. 8,734,026, issued May 27, 2014, both of which are hereby incorporated by reference in their entirety.
In a typical subsea communication network having a plurality of wellheads a large subsea control module is employed to manage and facilitate communications between one or more subsea devices and other equipment on the surface over a CAN BUS network. The large subsea control module, which acts as the master device on the CAN BUS network, then manages communication between the surface and other subsea equipment such as wellheads, distribution units, and monitoring equipment over the CAN BUS network. The subsea control module, in some implementations, may also be configured to transform or convert signals from one form to another to facilitate communications between a plurality of subsea devices. For example, the subsea control module may be configured to convert optical input signals into electrical output signals or convert electrical input signals into optical output signals.
For most CAN BUS networks, multiple devices for managing optical CAN BUS signal transmission and for low to high speed CAN BUS conversion are needed to facilitate communication between all devices on the CAN BUS network. For example, an optical connection may be needed to provide a signal to devices a large distance away from the signal source, but these devices may only operate with an electrical signal input, so a conversion from optical to electrical may be needed. Currently, multiple devices must be used to first transmit the optical signal and then convert the optical signal to an electrical signal. Using multiple devices increases the number of failure points on the system and increases the cost and complexity associated with identifying and repairing a problem on the CAN BUS network. Additionally, placing the electronics and circuitry needed to perform these transmissions and conversions at the end points of the signal instead of in a single housing creates un-needed and undesirable redundancy and possible points of failure.
What is needed is a single device that combines optical CAN BUS and low to high speed signal conversion in a single housing.